Conventionally, there is a tablet feeder composed of a case support table on which a motor is placed, and a tablet storage case which can be mounted on or dismounted from the case support table. In this kind of the table feeder, when the motor is driven, a rotor disposed inside the tablet storage case is rotated via a plurality of gears so that tablets contained in its pocket can be discharged through a delivery passage.
In this tablet feeder, the tablets discharged from the tablet storage case are counted by a counting sensor provided on the delivery passage. There are a type of the counting sensor which maintains on state regardless of the mounting of the tablet storage case on the case support table, and a type of the counting sensor which is switched to on state only when the tablet storage case is mounted.
However, the counting sensor which constantly maintains on state may suffer erroneous operation due to external perturbations such as light from a fluorescent lamp while the tablet storage case is detached from the case support table. Also, the counting sensor which is switched to on state only when the tablet storage case is mounted on the case support table may suffer errors in the delivery quantity if tablets are accidentally dropped off before the mounting on the tablet storage case is completed and so these tablets are not detectable.